Problem: $ { {-3} \times \left[\begin{array}{rrr}{4} & {-2} & {-1} \\ {1} & {-2} & {2}\end{array}\right] = {?} } $
Solution: To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rrr}{-3}\times{4} & {-3}\times{-2} & {-3}\times{-1} \\ {-3}\times{1} & {-3}\times{-2} & {-3}\times{2}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rrr}{-12} & {6} & {3} \\ {-3} & {6} & {-6}\end{array}\right]}$